If an empty format string is supplied, such as -F "", make that imply -q and cancel -c, so that -F "" -F "%b %t %r %p %e" -M both will monitor both sides but only display the output side - which will be useful when ratio is added (#67).

src/include/pv.h

@@ -240,6 +240,7 @@ extern void pv_state_output_set(pvstate_t, int, const char *);
 extern void pv_state_average_rate_window_set(pvstate_t, unsigned int);
 extern void pv_state_set_terminal_supports_utf8(pvstate_t, bool);
 extern void pv_state_othermonitor_set(pvstate_t, pid_t, int, int);
+extern void pv_state_cancel_output_if_empty_format_string(pvstate_t);
 
 extern void pv_state_inputfiles(pvstate_t, unsigned int, const char **);
 extern void pv_state_watchfds(pvstate_t, unsigned int, const pid_t *, const int *);

src/main/main.c

@@ -325,6 +325,7 @@ static int pv__run_monitor(const char *program_name, pvstate_t state, pvside_t s
 	/*@+observertrans@ */
 	pv_state_inputfiles(state, 1, dummy_argv);
 
+	pv_state_cancel_output_if_empty_format_string(state);
 	return pv_main_loop(state);
 }
 
@@ -892,10 +893,12 @@ int main(int argc, char **argv)
 		break;
 	case PV_ACTION_TRANSFER:
 		/* Normal "transfer data" mode. */
+		pv_state_cancel_output_if_empty_format_string(state);
 		retcode = pv_main_loop(state);
 		break;
 	case PV_ACTION_STORE_AND_FORWARD:
 		/* Store-and-forward transfer mode. */
+		pv_state_cancel_output_if_empty_format_string(state);
 		retcode = pv__store_and_forward(state, opts, can_have_eta);
 		break;
 	case PV_ACTION_WATCHFD:

src/pv/loop.c

@@ -185,10 +185,6 @@ int pv_main_loop(pvstate_t state)
 	unsigned int file_idx;
 	bool output_is_pipe;
 
-	/* TODO: treat "-F ''" as "-q" so there's no extra blank line. */
-	/* TODO: if "-q", turn off "-c", again so there's no blank line. */
-	/* May need local no_display and cursor flags for this. */
-
 	/*
 	 * "written" is ALWAYS bytes written by the last transfer.
 	 *

src/pv/state.c

@@ -779,6 +779,18 @@ void pv_state_othermonitor_set(pvstate_t state, pid_t pid, int read_fd, int writ
 	state->control.othermonitor_write_fd = write_fd;
 }
 
+/* If the format string is set to an empty string, stop all display output. */
+void pv_state_cancel_output_if_empty_format_string(pvstate_t state)
+{
+	if (NULL == state->control.format_string)
+		return;
+	if ('\0' != state->control.format_string[0])
+		return;
+	debug("%s", "empty format string - setting no_display and turning off cursor positioning");
+	state->control.no_display = true;
+	state->control.cursor = false;
+}
+
 /*
  * Set the array of input files.
  */